Probing the symmetry energy of neutron-rich matter

Betty Tsang, NSCL/MSU

IWNDT in Honor of Prof. Joe Natowitz Texas A&M University, College Station, Texas, USA August 19-22, 2013

What a mess !

Adv. Nucl. Phys. 26, 91 (2001)

Nat

owitz

et a

l, PR

C65

034

618

(200

2)

E*/A

Tem

pera

ture

A=180-240

A=140-180

A=100-140

A=60-100

A=30-60

B.A. Li, out of context

IntroductionSummary of ICNT workshops and NuSYM13.Updates of constraints on symmetry energyNew results from workshop relevant to HIC program

A way forward for high energy HIC:Theoretical challenges

Theoretical errorsTransport models

Heavy Ion Collisions at high energy; E/A>100 MeVp - /p+ ratios and flow; charge particles n/p yield

ratios and flow – new detectors Summary and Outlook

Probing the symmetry energy of neutron-rich matter

Nuclear Equation of State of asymmetric matter E/A (,) = E/A (,0) + 2S() = (n- p)/ (n+ p) = (N-Z)/A

...183

)(2

0

0

0

0

sym

o

KLSS symB

sym PE

LB

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330

Density dependence of symmetry energy

NuSYM10: RIKEN, July 26-28, 2010

NuSYM11: Smith College, July 26-28, 2011

NuSYM13: NSCL/FRIB, July 22-26, 2013

NuSYM14: Liverpool, July 7-9, 2014

NuSYM13—International Symposium on in Nuclear Symmetry EnergyNSCL/FRIB, East Lansing, MI July 22-26, 2013

http://www.nucl.phys.tohoku.ac.jp/nusym13/index.html

B.A. Li, out of context

NuSYM10

Tsang et al. C 86, 015803 (2012)NuSYM11

heavy ion collisionsPRL 102,122701(2009)

p elastic scatteringPRC82,044611(2010)

Isobaric Analogue StatesNPA 818, 36 (2009)

neutron-star radiusPRL108,01102(2012)

Pygmy Dipole ResonancesPRC 81, 041304 (2010)

Finite Droplet Range ModelPRL108,052501(2012)

...183

2

0

0

0

0

BsymB

osym

KLSE

Consistent Constraints on Symmetry Energy from different experiments HIC is a viable probe

Constraints from reactions Constraints from structureNuSYM13

Updated Constraints from NuSYM13 (in progress)

Updated Constraints from NuSYM13 (in progress)

NuSYM10 NuSYM13

Updated Constraints from NuSYM13 (in progress)

Updated Constraints from NuSYM13 (in progress)

Observation:MNS ~ 2Msun

RNS ~ 9 km

Equation of Statestiff EoS at high softening EoS at ~20

Astrophysics and Nuclear Physics

Skyrme interactionsNeutron star

Astrophysics and Nuclear Physics

Observation:MNS ~ 2Msun

RNS ~ 9 km

Equation of Statesoftening EoS at ~ 20

stiff EoS at high

HIC

AV14+UVII Wiringa, Fiks, & Fabrocini 1988Neutron star (Rutledge, Gulliot)

Constraints on the density dependence of symmetry energy

Au+Au

n,p squeeze-out

p+/p- ratios

Isospin Diffusion

Problems at high density

Antisymmetrized Molecular Dynamics (AMD)

Xe

+ Sn

; E/

A=5

0 M

eV

With cluster correlations

Without cluster correlations

Transport Model:

• Different codes/models predict different outcomes (flow vs. pions stiff vs super-soft)

• Transport input parameters need to be better determined

• Cluster formation affects reaction dynamics (and the observables)

Problems also exists in LE

Akira OnoNuSYM11

A Way Forward – Transport modelsTransport Model:

• Different codes/models predict different outcomes (pion vs. flowstiff vs super-soft)

• Transport input parameters need to be better determined

• Cluster formation affects reaction dynamics (and the observables)

Problems also exists in LEAntisymmetrized Molecular Dynamics (AMD)

Xe

+ Sn

; E/

A=5

0 M

eV

With cluster correlations

Without cluster correlations

Transport workshop (China) :

• Comparison of codes – clarify the differences between versions of codes

• Comparison of models• Effects of transport input parameters

should be studied systematically• Establishment of benchmark tests and

benchmark data• Implementation of better cluster

formation in transport models

A Way Forward – DataData – Ratio observables from RIB :• Choose observables that are less

sensitive to the assumptions of the transport models

• New observables (p+/p- ratios) requires new detectors

Data (Current Status)Au+Au experiments were performed in 90’s to study the symmetric matter EOS

n,p squeeze-out

p+/p- ratios

0.8

0.9

1

1.1

1.2

1.3

0 20 40 60 80 100 120 140

Central Sn+Sn collisionsE/A = 300 MeV

=0.5=1.0=2.0

M(p

- ,132

+124

)/M(p

- ,108

+112

)

KEcm

(MeV)

MSU-TAMU-RIKEN-Kyoto initiative: Time Projection Chamber to detect pions, charged particles at ~20

chamber

Beam

Thin-Walled EnclosureProtects internal components, seals insulation gas volume, and supports pad plane while allowing particles to continue on to ancillary detectors.

Rigid Top PlatePrimary structural member,reinforced with ribs.Holds pad plane and wire planes.

Pad PlaneMounted to bottom of top plate. Used to measure particle ionization tracks

Field CageDefines uniform electric field.Contains detector gas.

Voltage Step-DownPrevent sparking from cathode (20kV) to ground

Wire PlanesMounted below pad plane.Provide signal multiplication and gate for unwanted events

RailsFor inserting TPC into SAMURAI vacuum chamber

SAMURAI TPC: Exploded ViewFront End ElectronicsSTAR FEE for testing,ultimately use GET

Target Mechanism

Calibration Laser Optics

Cosmic ray tracks

Cosmic Event 0: July 24th, 2013 @NSCL

Figure courtesy of GET collab.

10.5 bit dynamic range1KHz – 10Gb/s

GET electronics (256 channels): 7/27/13

STAR electronics (1024 channels): 5/15/13

Heavy Ion Collisions at high density with RIBOld data: Au+Au, E/A=150 to 1500 MeV

New Experiments at RIB facilities

6.5 days approved by June RIKEN PAC

SUMMARY• Consistent constraints on the symmetry energy at sub-

saturation densities with different experiments suggest that heavy ion collisions provide a good probe at high density..

• Astronomical observations suggests the importance of probing ~20 region.

• At high & low densities: transport workshop is being organized to examine the transport codes.

• Experiments to measure constraints on the symmetry energy above saturation densities have started with n/p ratios and will continue with pion and flow measurements with the TPCs at RIKEN and FRIB.

NuSYM13, July 22-26, 2013, East Lansing, USA

SPiRIT TPC: Status and experimental program

R. Shane, for the S-TPC collaboration

SAMURAI Pion-Reconstruction and Ion-Tracker TPC

Topical Theory Programs complement to INT and ECT*MSU, GSI, & RIKEN directors contribute $50k/year to

host 10-20 theorists get together for 2-4 weeks.In Nov. 2012, the ICNT board recommended 3 proposals NSCL/FRIB -- Chuck Horowitz: Symmetry-energy in the context

of new radioactive beam facilities and astrophysics GSI -- Lucas Platter: Halo Physics at the Neutron Drip Line...

(approved by the EMMI PAC in May) RIKEN -- Michael Famiano: Element Genesis and Cosmic

Evolution (delayed due to lack of funding at RIKEN)

ICNT—International Collaborations in Nuclear Theoryhttp://frib.msu.edu/content/ICNT

Topical Theory Programs complement to INT and ECT*MSU, GSI, & RIKEN directors contribute $50k/year to

host 10-20 theorists get together for 2-4 weeks.In Nov. 2012, the ICNT board recommended 3 proposals NSCL/FRIB -- Chuck Horowitz: Symmetry-energy in the context

of new radioactive beam facilities and astrophysics

ICNT—International Collaborations in Nuclear Theoryhttp://frib.msu.edu/content/ICNT

Week I (July 15 - 19): Symmetry energy at low nuclear densitiesWeek II (July 22 - 26): NuSYM13Week III (July 29 – Aug 2): Symmetry energy at high densities including astrophysical environment.Week IV (Aug 5 - 9): Future DirectionsDeliverable: Write-up of a document (what have we

(Horowitz, Danielewicz, Li, Onishi, Ono, Tsang) done with Konrad’s $50k?)

Facility for Rare Isotope Beams (FRIB)

FRIB will provide intense beams of rare isotopes (that is, short-lived nuclei not normally found on Earth). FRIB will enable scientists to make discoveries about the properties of these rare isotopes in order to better understand the physics of nuclei, nuclear astrophysics, fundamental interactions, and applications for society.